Recently, wireless charging technology or non-contact charging technology has been developed and has been widely utilized in various electronic devices. The wireless charging technology is a system that uses wireless power transmission and reception in which, for example, the battery of a mobile phone may be automatically charged by simply placing the mobile phone on a charging pad without connecting to a separate charging connector. The wireless charging technology can enhance the waterproof function by wirelessly charging the electronic products, and can improve the portability of electronic equipment because a wired charger is not necessary.
Among them, charging by using a resonance method is performed as follows. When a wireless power receiver (e.g., a mobile terminal), which requires charging, is positioned on a wireless power transmitter (e.g., a charging pad), which transmits wireless power, the wireless power transmitter may charge the wireless power receiver. In the case where a plurality of wireless power receivers are placed in a charging area of a single wireless power transmitter, there may be a difference between the power that is necessary for respective wireless power receivers and the transmission power, so respective wireless power receivers are required to be efficiently charged.